Method of controlling trench microloading using plasma pulsing

Abstract

Methods and apparatus for controlling microloading, such as within cell microloading between adjacent cells or isolated/dense microloading between areas of isolated or dense features during shallow trench isolation (STI) fabrication processes, or other trench fabrication processes, are provided herein. In some embodiments, a method for fabricating STI structures may include providing a substrate having a patterned mask layer formed thereon corresponding to one or more STI structures to be etched; etching the substrate through the patterned mask layer using a plasma formed from a process gas to form one or more STI structure recesses on the substrate; and pulsing the plasma for at least a portion of etching the substrate to control at least one of a depth or width of the one or more STI structure recesses.

1 . A method for fabricating shallow trench isolation (STI) structures, comprising:
 providing a substrate having a patterned mask layer formed thereon corresponding to one or more STI structures to be etched;   etching the substrate through the patterned mask layer using a plasma formed from a process gas to form one or more STI structure recesses on the substrate; and   pulsing the plasma for at least a portion of etching the substrate by pulsing a biasing power and a source power to control at least one of a depth or width of the one or more STI structure recesses.   
     
     
         2 . (canceled) 
     
     
         3 . The method of  claim 1 , wherein at least one of the biasing or source power is pulsed at a pulse frequency of about 200 Hz to about 100 kHz. 
     
     
         4 . The method of  claim 1 , wherein at least one of the biasing or source power is pulsed at a duty cycle of about 10% to about 95%. 
     
     
         5 . The method of  claim 1 , wherein the biasing and source power are pulsed in synchronization. 
     
     
         6 . The method of  claim 1 , wherein the biasing and source power are pulsed out of phase. 
     
     
         7 . The method of  claim 1 , wherein at least one of the biasing power or source power is an RF signal or DC signal. 
     
     
         8 . The method of  claim 1 , wherein the biasing power is provided at a power between about 100 to about 900 W at about 400 kHz to about 60 MHz. 
     
     
         9 . The method of  claim 1 , wherein the source power is provided at a power between about 300 to about 2000 W. 
     
     
         10 . The method of  claim 1 , wherein pulsing the plasma further comprises:
 maintaining the plasma continuously for a first period of time; and   pulsing the plasma for a second period of time.   
     
     
         11 . The method of  claim 10 , wherein the first period of time is about 3 to about 300 seconds and the second period of time is about 3 to about 300 seconds. 
     
     
         12 . The method of  claim 1 , wherein the patterned mask layer corresponds to a node size of about 40 nm or smaller and is formed via a self-aligned double patterning process. 
     
     
         13 . The method of  claim 1 , wherein the one or more STI structures further comprise:
 a plurality of STI structures grouped into a first region having a first density of one or more first STI structures and a second region having a second density of one or more second STI structures, wherein the second density is greater than the first density.   
     
     
         14 . The method of  claim 13 , further comprising:
 controlling a ratio of the etch depth of the first STI structures in the first region to the etch depth of the second STI structures in the second region by pulsing the biasing power and the source power.   
     
     
         15 . The method of  claim 14 , further comprising:
 etching each of the first and second STI structures to a substantially equivalent depth.   
     
     
         16 . The method of  claim 1 , wherein the substrate further comprises:
 one or more intervening layers disposed between the substrate and the patterned mask layer.   
     
     
         17 . The method of  claim 16 , wherein at least one layer of the one or more intervening layers comprises polysilicon. 
     
     
         18 . (canceled) 
     
     
         19 . The method of  claim 1 , wherein the process gas comprises at least one at least one of a fluorine-containing gas or a fluorocarbon- or hydrofluorocarbon-containing gas. 
     
     
         20 . The method of  claim 19 , wherein the process gas further comprises an inert gas, wherein the inert gas comprises at least one of nitrogen (N 2 ), helium (He), or argon (Ar). 
     
     
         21 . The method of  claim 15 , further comprising:
 controlling etch depth microloading of individual second STI structures in the second region with respect to each other by pulsing the biasing power and the source power.   
     
     
         22 . A method for fabricating shallow trench isolation (STI) structures, comprising:
 providing a substrate having a patterned mask layer formed thereon corresponding to a plurality of STI structures to be etched, wherein the plurality of STI structures comprise a plurality of first STI structures disposed in a first region having a first density of first STI structures and a plurality of second STI structures disposed in a second region having a second density of second STI structures, wherein the second density is greater than the first density;   etching the substrate through the patterned mask layer using a plasma formed from a process gas to form a plurality of STI structure recesses on the substrate; and   pulsing the plasma for at least a portion of etching the substrate by pulsing a biasing power and a source power to control etch depth microloading of individual second STI structures in the second region with respect to each other by pulsing the biasing power and the source power.